Reflecting optical system capable of compensating for the variation in polarization mode

ABSTRACT

A REFLECTING OPTICAL SYSTEM WHICH COMPRISES TWO REFLECTING SURFACES SUCH AS MIRRORS OR THE LIKE EQUAL IN OPTICAL CHARACTERISTICS DISPOSED TO HAVE THE SAME PLANE OF INCIDENCE. A FIRST HALF-WAVELENGTH PLATE IS DISPOSED IN THE PATH OF LIGHT BETWEEN THE TWO REFLECTING SURFACES PERPENDICULARLY TO THE PATH OF LIGHT AND IN SUCH A MANNER THAT THE AXIS OF THE FIRST PLATE FORMS AN ANGLE OF 45* WITH RESPECT TO THE PLANE OF INCIDENCE OF THE FIRST REFLECTING SURFACE AND IF DESIRED, A SECOND HALF-WAVELENGTH PLATE IS DISPOSED IN THE PATH OF EMERGENT LIGHT FROM THE SECOND REFLECTING SURFACE PERPENDICULARLY TO THE OPTIC AXIS OF THE PATH OF EMERGENT LIGHT IN SUCH A MANNER THAT THE AXIS OF THE SECOND PLATE FORMS AN ANGLE OF 45* WITH RESPECT TO THE PLANE OF INCIDENCE OF THE SECOND REFLECTING SURFACE, WHEREBY THE LIGHT EMERGENT FROM THE OPTICAL SYSTEM IS ALWAYS ENSURED TO PRESENT TO SAME MODE OF POLARIZATION AS THAT OF THE INCIDENT LIGHT.

BSO-405 LTI NG Filed Dec. 23', 1970 United States Patent IOffice3,675,986 Patented July 11, 1972 U.S., Cl. 350-157 2 Claims ABSTRACT OFTHE DISCLOSURE A reflecting optical system which comprises tworeflecting surfaces such as mirrors or the like equal in opticalcharacteristics disposed to have the same plane of incidence. A firsthalf-wavelength plate is disposed 'in the path of light between the tworeflecting surfaces perpendicularly to the path of light and in such amanner that the axis of the first plate forms an angle of with respectto the plane of incidence of the first reflecting surface. 2

And if desired, a second half-wavelength plate is disposed in the pathof emergent light from the second reflecting surface perpendicularly tothe optic axis of the path of emergent light and in such a manner thatthe axis of the second plate forms an angle of 45 with respect to the 3plane of incidence of the second reflecting surface, whereby the lightemergent from the optical system is always ensured to present to samemode of polarization as that of the incident light.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a reflecting optical system of the type which is capable ofcompensating for the variation in polarization mode between the lightsincident on and emergent from the optical system.

Description of th` prior art It is widely known that light as it isreflected by a reflecting surface such as mirror or the like presents amode of polarization different from that presented by light as it isincident on the reflecting surface. To solve this problem, the prior arthas sometimes resorted to the use of a compensating plate or the likewhich vary the mode of polarization of the emergent light so as tocompensate for the variation in polarization mode between the incidentand (R1, o (cos 0 0 R, sin 0 system capable of compensating for thevariation in polarization mode comprises first and second reflectingsurfaces equal in optical characteristic which are disposed to have thesame plane of incidence. According to one aspect of this invention, afirst half-wavelength plate is disposed in the path of light betweensaid two reflecting surfaces perpendicularly to the optic axis of saidpath of light and in such a manner that the axial orientation of saidfirst plate forms an angle of 45 with respect to the plane containingthe incident optic axis and the normal of said first reflecting surface.According to further aspect, a second half-wavelength plate is furtherdisposed in the path of emergent light perpendicularly to the optic axisof said path of emergent light and in such a manner that the axialorientation of said second plate forms an angle of 45 With respect tothe plane of incidence of said second reflecting surface.

The above features of the present invention will become more apparentfrom the following description of an em- 0 bodiment thereof when takenin conjunction with the ac-v companying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration ofthe reflecting optical 5 system according to a first embodiment of thepresent invention; and FIG. 2 shows a second embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. l, whichshows a first embodiment, reflecting surfaces M1 and M1 such as mirrorsor the like having equal optical characteristic, particularly equalpolarization characteristic are disposed to have the same incidentsurface. In the path of light between the two refleeting surfaces M1 andM2, there is disposed a halfwavelength plate H1 perpendicularly to theoptic axis of that path of light and in such a manner that the axialorientation of the plate H1 forms an angle of 45 with respect to theplane of incidence of the reflecting surface M1, i.e. the planecontaining the incident optic axis and the normal of the reflectingsurface M1.

In FIG. l, B1 and B2 show incident light and emergent lightrespectively, and said two reflecting surfaces M1 and M2 and thehalf-wavelength plate H1 constitute a reflecting optical systemgenerally indicated by A.

Description will now be made as to how the polarization of the emergentlight beam B2 has the constant relation with that of the incident lightbeam B1.

If the incident light beam B1 is divided into two cornponents, i.e. thecomponent in the plane of incidence and the component in the verticalplane, the polarization of the incident light beam B1 at is passesthrough the reflecting optical system A may be analyzed by the use ofJones matrix, as follows:

-sin0) (l 0)( cos sin 6) Rpo cos@ 0 -1 -sin cos@ 0R. y :c

emergent lights. However, this has involved adisadvantage where x=Rpe1P,y=R5e1", Rp and R,1 represent the rethat the amount of compensationprovided by such compensator must be varied in acordance with the changeof the mode of polarization presented by the incident light.

come such a disadvantage peculiar to the conventional reflecting opticalsystem and provide a novel reflecting optical system which alwaysensures light emergent from the reecting optical system to present thesame mode of polarization as that of the light incident on that system.According to the present invention, the reflecting optical fiectedcomponents in the plane of incidence and the vertical plane of thereflecting surfaces M1 and M1, respectively, and 6 represents the angle(45) which the axial orientation of the half-wavelength plate H1 formswith respect to the planes of incidence of the respective reflectingsurfaces M1 and M1.

As will be seen from the foregoing equation, the mode of polarization ofthe emergent light beam B1 is in the constant relation with that of theincident light beam B1.

Thus, according to the present invention, there is provided a reflectingoptical system which always ensures the light emergent from the opticalsystem to present the fleeting optical system A is analyzed by the useof Jones matrix as follows:

(cos sin 0) (l 0) cos 0) (sin 0 R1, 0

sin 6 cos 0 0 -1 sin 0 cos 0) 0 Rs) (e050 -sin 6) (l 0)( cos 6) (sin 0)R1, 0 (z) x sin 0 cos 9 0 -sin 6 cos 0 0 Rl y (y) mode of polarizationhaving the constant relation with where x=Rpei"P, y=R1seiS, Rp and R1represent the retlie light incident on the optical system, independentlyof 10 lected components in the plane of incidence and the the variable'mode of polarization occurring in the latter. vertical plane of thereilecting surfaces M1 and M2, re-

spectively, and 0 represents an angle (45) with the axial orientationsof the half-wavelength plates H1 and H2 form with respect to the planesof incidence of the reilecting surfaces M1 and M2.

As apparent from the above equation, the polarization The respectiveorientations of the reccting surfaces are symmetrical relative to thehalf-wavelength plate, and when the incident light is rightly polarizedlight, then the emergent light is leftly polarized light and both havethe same value of ellipticity.

In FIG. 2, there is shown a second embodiment, in hf tile .metrglnthhtbegun B2 s quite equal to that of which the reflecting surfaces M1 andM2 have the Same ecln, lg gam 1' opticalcharacteristics especially inits' polarization char- 20 1. A reecting Optical system capable ofcompensating acteristic and are disposed as symmetrical with respect tofor the variation in polarization mode comprising first thehalf-wavelength plate H1. In the path of light between and Secondreflecting Surfaces having the same optical the tWO refiecting SurfacesMi and Mz, there iS disposed a characteristics and disposed to have thesame incident haifWaVeiength Piate Hons mentioned in the nist embodi'surface, a half-wavelength plate disposed in the path of ment. In theSecond embodiment, there iS disposed anlight between said two reneetingsurfaces perpendiculariy other half-wavelength plate H2 in the path ofemergent to the optical axis of said path of light, the axialorientalight from the reflecting surface M2 perpendicularly to tion ofthe plate forming an angle of 45 degrees with the optical axis of thatpath of emergent light and in such respect t0 the Piane including theincident light aXiS irld a manner that the axial orientation of theplate H2 forms the normal of .the first reflecting Snrfnce- U an angleof with respect to the plane of incidence of 30 2 A reflecting opticalSYStem according t0 cialrri 1,

reecting surface M2. Thus, an incident light beam B1 is rewherem Saidrst and Second reecfmg Surfaces oppsed ected by the reecting surface M1to reach the other reto eaclll omer sfymmemcaus.' and th? mcldent an.demergfmt M2 the H1 satisfaga alargararrastrar and me dlrected as anemergent hght beam B2 from the 35 other half-wavelength plate disposedin the path of emerreflecting surface M2 through the otherhalf-wavelength gent light from Said second reecting Surface perpendcwplate H2 in the manner as shown- The tWo reflecting sur' larly to theoptic axis of said path of emergent light and faces M1 and M2 tOgether'With the tWO half-Wavelength the axial orientation of said another plateforms an angle Plates H1 and H2 constitute reflecting Surfaces M1 and M2of 45 degrees with respect to the light of incidence of together withthe two yhalf-wavelength plates H1 and H2 40 Said Second reectingSurface constitute a reecting optical system of the present inventiongenerally indicated by the letter A. References Cited Now it isexplained that the emergent light beam B2 UNITED STATES PATENTS presentsthe same mode of polarization as that presented by the incident lightbeam B1 in the above-described 45 3510'198 5/1970 Pace' reccting opticalSYStem A'- DAVID SCHONBERG, Primary Examiner If the incident light beamB1 is divided into two com- P R MILLER Assistant Examiner ponents, i.e.the component in the plane of incidence and the component in thevertical plane, the polarization of U S CL XR. the incident light beamB1 as it passes through the re- 350 147, 152, 233

UNTTED STATES PATENT OFTTCE CERTIFICATE 0F CORREC'HGN l Patent No. 3 675986 Dated July ll, 1972 Inventor(s) 'Iadaki Yamamoto and Toshiyuki KasaiIt is eertified that error appears in the aboveidentified patent andthat said Letters Patent are hereby Corrected as shown below:

Col. 2, lines 57 through 59, the formula should read as follows:

Rp o cos 6 -sin 6 l o .cose sin@ Rp o `0 Rs sin 9 lcos 6 0' -1 -sin cosS0` RS Col. 4, lines 3 through 8, the formula should read as follows:

cos@ -sinS l 0 cose sin Rp 0 cos@ -sinG d: O

sin@ cos@ O -l -sine cose 0 Rs sin@ cosG O -l Signed and sealed this 8thday of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C, MARSIIALL DANN Attesting Officer Commissioner ofPatents FORM P04050 (1059) uscoMM-oc aoa7e-pe9

